Beam pointing stability is critical to maintaining a calibration state of a spectrometer and laser power impinging upon an optical detector within spectrometers that utilize lasers, such as tunable diode lasers (TDL), as their light sources. Optical elements, such as laser lenses, are often used to steer beams emitted by the lasers along a particular beam path within a sample cell for detection by a detector. However, fluctuations in ambient temperatures can cause the thermal expansion of a laser lens mounting fixture to change the relative alignment of the laser lens to the laser, which, in turn, has a negative impact on laser beam alignment stability. These temperature fluctuations are particularly problematic in typical spectrometer field installations, especially in climates having large temperature swings such as deserts and the like.
Additionally, especially for TDL spectrometers requiring short focal length lenses, the temperature of the laser lens can influence the temperature of the laser, causing a wavelength shift with ambient temperature, also known as laser drift, which can result in an offset from the state of calibration of the spectrometer. In a typical application, such as described in co-owned US patent (insert reactive gas patent number for differential spectroscopy) such detrimental laser wavelength shifts can occur with laser temperature changes in the order of single digit mK. This thermal influence on the TDL is typically undetected by the temperature sensor used to control the laser set-point temperature, making it impossible to correct with a controller.